Stabilized methylene chloride composition

ABSTRACT

Methylene chloride stabilized by admixture with diisopropylamine, N-methyl pyrrole, butylene oxide, propylene oxide, methyl acetate, acetone, tertiary amylenes, and methyl alcohol. The composition is useful in metal degreasing.

United States Patent Beckers Aug. 5, 1975 STABILIZED METHYLENE CHLORIDE COMPOSITION [56] References Cited [75] Inventor: Norman L. Beckers, Humble, Tex. UNITED STATES PATENTS 1,904,450 4/l933 Harris 260/6525 R [73] Ass'gnee' 't' Cmporamn 2,981,759 l/l96l Cole, Jr. et a]. 260/6525 R Cleveland, Ohio [22] Filed: May 13, 1974 Primary E.\'amin'erD. Horwitz App]. No; 469,333

Related US. Application Data Continuation-impart of Ser. No. 335,002. Feb. 23, 1973. abandoned, and a continuation-in-part of Ser. No. 335,003. Feb. 23, 1973, abandoned.

US. Cl 260/6525 R C07c 17/40 Field of Search 260/6525 R Attorney, Agent, or Firm-William A. Skinner [57] ABSTRACT 2 Claims, No Drawings STABILIZED ETI YLENE CHLORIDE coMPosITIoN g cRoss REFERENCE To RELATED APPLICATIONS This is a continuation-in-partof copending ai;)plications Ser. No. 335,002 and Ser.,No..335,003, bothfiled Feb. 23, 1973 andnow abandoned. 7

BACKGROUND OF'THE INVENTION Methylene chloride is a highly versatile and useful solvent for various industrial applications at both normal and. elevated temperatures. A particularly important industrial use is the vapor degreasing of metals. Methylene chloride is known to be more stable than other chlorinated hydrocarbon solvents such as perchloroethylene, trichloroethylene and methyl chloroform when the solvents are used in unstabilized condition. For example, methylene chloride is more resistant to oxidation, hydrolysis and pyrolysis than other chlorinated solvents and does not substantially react with aluminum in the aluminum scratch test commonly used to indicate unstabilized or minimally stabilized methyl chloroform. In addition, methylene chloride may be used to greater advantage in vapor degreasing of metals than other known degreasing solvents since it may be used effectively at lower temperatures due to its lower boiling point and excellent stability. Methylene chloride is particularly desirable for such degreasing operations since it is substantially resistant to photochemical activity and therefore does not contribute to air pollution by smog formation.

However, methylene chloride when used in various metal cleaning functions, including vapor degreasing, suffers the disadvantage of being reactive with aromatic and aliphatic organic compounds in the presence of metals, metal halides and combinations thereof. The

reaction produces hydrochloric acid and objectionable high boiling tarry substances which render the methylene chloride unsuitable for further use. The entire reaction of methylene chloride inthe presence of aromatic compounds is not completely understoood but is believed to be a condensation reaction catalyzed by metal, metal halides or combinations thereof. Likewise, the aliphatic compound reaction is believed to be catalyzed, or initiated and catalyzed by the presence of metals such as aluminum, zinc, iron and the like, halides of said metals and combinations of said metals and halides.

Aromatic and aliphatic organic compounds of this reactive nature and metals such as aluminum, iron and zinc, their halides and combinations are generally introduced into the methylene chloride from various cutting oils and lubricants used in metal fabricating operations which are carried over into the methylene chloride solvent during vapor degreasing or other cleaning of the fabricated metal parts. Solvent manufacturing, handling and storage equipment is another source for introduction of such impurities. To prevent degrada-' tion and other types of deterioration such as oxidation,

hydrolysis and pyrolysis which may occur in some :in stances, has been the practice to incorporatem'inor quantities of various organic compounds into methyl} ene chloride, which compounds act as stabilizers to su bstantially pr ev ent suchdegradation. It is desirable-to provide methylene chloride stabilized to effectively prevent degradation in various applications, and thev demand still exists for a low cost stabilized methylene chloride composition that cari beeasilyprepared and which provides optimum stabilization under many different operating conditions. U

'"SUMMARY OF THE INVENTION 'An object of this invention is to provide a stabilized methylene. chloride composition which-does not deteriorate or degrade when association with metals, metal halides and combinations including aluminum, iron and zinc, halides of said metals and combinations, and aromatic or aliphatic compounds. M v

A further object of this invention is to provide a stabilized methylene chloride composition in which the stabilizers are low in cost and capable of being incorporated with ease into the methylene chloride.

Still another object of this invention is to provide a process for the degreasing of metals by contacting the metals with methylene chloride stabilized to prevent degradation of the methylene chloride in the presence of impurities such as reactive aromatic and aliphatic compounds and metals, halides of said metals and combinations of the individual metals and salts thereof.

These and additional objects of the present invention will become apparent to those skilled in the art from the description and claims which follow;

DESCRIPTION OF THE PREFERRED EMBODIMENTS The objects set forth above have been found to be attained by providing a stabilized composition consisting essentially of methylene chloride containing from about 0.001 to about 2.0 percent by weight of the methylene chloride of each of diisopropylamine, N- methyl pyrrole, butylene oxide, propylene oxide, methyl acetate, acetone, tertiary amylenes and methyl alcohol. 1

The quantity of the stabilizing agents useful in the practice of this invention will vary depending upon the conditions of use, the identity and quantity of other stabilizers incorporated into the methylene chloride and other practical operating considerations. Each stabilizing agent or compound may generally be used within the range of from about 0.001 to about 2.0 percent and preferably from about 0.002 to 1.0 percent by weight of the methylene chloride. Although higher concentrations may be used, if desired, no additional benefit is obtained andthe cost is unnecessarily increased. While ride contains an admixture of stabilizing amounts of di-- isopropylamine, -N-methy1 pyrrole, butylene oxide, propylene. oxide, methyl acetate, acetone, tertiary amylene and methy alcohol.

In degreasing metals, with the above de scribed .pre-

ferred stabilized methylene chloride, the presence of aromatic or aliphatic organic compounds and metals,

metal halides and combinations thereof will not cause degradation of the methylene chloride. The presence of reactive aromatic organic compounds such as toluene, mesitylene, napthalene, durene and the like, as well as aliphatic compounds such as trans-dichloroethylene, carbon tetrachloride, 1,1,l-trichloroethane and the like, is usually attributed to the use of cutting oils and lubricants during metal fabrication operations and to contamination during solvent manufacturing, handling and storage. The presence of metals including aluminum, iron, zinc, halides of such metals and combinations thereof is usually attributed to fabricating operations such as stamping, drilling, or machining. Degradation of methylene chloride during degreasing operations where reactive organic compounds and metals are 15 suits of of substantially water free methylene chloride in a 300 ml flask, adding about 1.0 grams of 20 mesh granular aluminum and suspending a bright aluminum coupon about 2 X 7 cm in a condenser fitted to the flask. Methylene chloride containing 5 percent by volume of various organic compounds and methylene chloride with the stabilizing composition of this invention plus 5 percent by volume of organic compounds were refluxed for varying time periods. During the extended period of reflux the solvent vapor surrounded, condensed, and dripped from the suspended strip. In all cases the pH was determined after the system was refluxed for the varying time periods noted and visual observations of the aluminum condenser coupon were made. The rethe various tests are shown in Table 1 below.

TABLE I EFFECT OF ORGANIC COMPOUNDS ON ALUMINUM REFLUX STABILITY TESTS VVlTH METHYLENE Example Solvent No. System 1 Methylene Chloride Methylene Chloride Methylene Chloride plus Aluminum Coupon, Stabilized With 0.0025 Wt.% Diisopropylarnine 0.005 Wt.% N-methyl pyrrole 0.25 Wt.% Propylene Oxide 0.125 Wt.% Butylene Oxide 0.20 Wt.%

Methyl Acetate 0.05 Wt.%

Acetone Tert. Amylenes 0.05 Wt.%

Methyl Alcohol Methylene Chloride Methylene Chloride Volume. Additive 5% Mesitylene 5% Mesitylene 5% Durene 5% l l 1 Trichloroethane Methylene Chloride plus Aluminum Coupon, Stabilized with system of Example 3 Same as Example 6 with addition of about 0.0 g. anhydrous AlCl and one additional day of reflux Same as Example 7 with addition of about 0.04 g. anhydrous FeCl;, and seven additional days of reflux 5% 1,1,1- Trichloroethane 5% l l 1- Trichloroethane 5% l, l l- Trichloroethane CHLORIDE Days Test Condenser Coupon Corrosion Color pH Solvent 3 7.0 Clear and Blisters Colorless Orange-Black, HCl fumes Clear and Colorless 5 3 Generally Severe None Generally Severe Severe Yellow, turbid Black HCl fumes Clear and None Colorless Clear and None Colorless Clear and None yellow The tests in Table l were conducted by venting the condenser to room air and without the addition of water. Also in Table l the pH determinations were made with a portion of the water'layer obtained by extraction of the solvent with water equal to the volume of the solvent system.

Table l illustrates the prevention of degradation of methylene chloride by the stabilizing components of this invention in the presence of aluminum and the aromatic compound mesitylenc (trimethyl benzene) in Example 3. Examples 2 and 4 show degradation of methylene chloride in the presence of the aromatic compounds mesitylene and durene (tetramethyl benzene) 4 when refluxed with aluminum in the absence of the stabilizing composition of this invention.

In Example 5 deterioration of the solvent system occontents of the Soxhlet and of the flask were determined from aportion of the aqueous phase obtained by extraction of the solvent with an equal volume of neu- 5 tral distilled water after the solvent system had been recurred due to the reaction of aluminum with the confluxed for the time specified. The zinc and iron coutamed l, l ,l-trichloroethane. In Example 6 the addition pons were cleaned of any accumulated corrosion prodof the stabilizing composition of this invention to this ucts, weighed and the difference in initial and final solvent system prevented such deterioration and in Exweight recorded as weight loss. ample 7 even after about 0.04 grams anhydrous alumi- 10 The results are shown below in Table II.

TABLE II Stabilized Alk. as Example Solvent Days pH ppm. NaOH Color of Total mg. Loss No. System Test Flask Sox. Flask Sox Solvent Zn (Sox.) Fe (Cond.)

9 Methylene Chloride I5 9.2 7.4 18 4.3 Clear, gray 36 140 plus 0.30 Wt.% Propylene Oxide 0.10 Wt.% Butylene Oxide 0.005 Wt.% Diisopropylamine 0.005 wr.% N- methyl pyrrole l0 Methylene Chloride 8.5 7.3 16 3.7 Clear, gray 28 54 plus Aluminum Coupon Stabilized With 0.0025 Wt.% Diisopropylamine 0.005 Wt.7z N-methyl pyrrole 0.25 wuz Propylene Oxide 0.125 Wt.% Butylene Oxide 0.20 Wt.% Methyl Acetate 0.05 wmz Acetone 0.25 Wt.7c Tert. Amylenes 0.05 WW Methyl Alcohol num chloride was added and the system refluxed an ad- The superiority of the stabilizing composition of this ditional day. In Example 8 even with the further addiinvention is evidentffrom a comparison of the results of tion of about 0.04 grams anhydrous ferric chloride and Example 10, the composition of the present invention, an additional seven days of refluxing no corrosion of and Example 9, a stabilizing composition of known the aluminum in the flask or the condenser was obgood stabilizing;characteristics formulated by the appli- Served. cant herein. Much less corrosion of the zinc coupon in In Table II hydrolytic stability tests were made by the Soxhlet and:the iron coupon located in the conplacing I ml of partially stabilized methylene ehlodenser occurred'in the use of the composition of this ride in Example 9 and 150 ml of methylene chloride invention during the 15 day reflux period. g the 3 56 if g i l i g i m In Examples 11 and 12 of Table III reflux stability anciip e h into all m 01mg as d i h 50 tests were conducted by following Federal Specifica- L extacmrdeqmppe W 9 tion 0-T-236b modified by the use of 200 ml of the solrea d con enser veme to room I y 1 vent system in place of 100 ml and by positioning a 6- tders g s g E eachd ig first watt ultraviolet lamp about 1 inch from the vapor tube ag g t e s 0 f was L en of the Soxhlet extraetor. A 300 ml boiling flask was fita e tggz o h mes ar d z) a ted with a Soxhlet extractor, a condenser connected to t gram 0 mes m ar zmc an about 0 the extractor, about 1.0 gram of granular zinc and Iron powder were placed in the flask, A X 7 Zmc about 0.5 ml of water was added to the flask and a 2 X Coupon of known f was Posmoned m the soxhlfzt 7 cm zinc coupon was inserted in the extractor and the and a 2 X 7 Cm we'ghed steel coupon was mounted m condenser. The condenser was vented to a water scrubthe condenser. The contents of the flask were refluxed 60 for the period of time specified by heating the boiling flask with an electric heater. At the end of the reflux ber.

The results of the tests are presented in Table Ill.

TABLE III REFLUX STABILITY TESTS WITH STABILIZED METHYLENE CHLORIDE Stabilized Metal Example Solvent in Days Color of Mg. Zinc Loss No. System Test Test pH Solvent Soxhlet Condenser l l Methylene Chloride Zn 16 Very l I 59 TABLE III-Continued REFLUX STABILITY TESTS WITH STABILIZED METHYLENE CHLORIDE Metal in Test Stabilized Solvent System Example Days No. Test pl-I 'I'urbid Zn 6.7 Turbid Storage stability tests of stabilized methylene chloride were carried out in Examples 13 to 15 of Table IV. About 250 ml of each of three stabilized methylene chloride compositions specified in the Examples was placed in a pint bottle containing three one-sixteenth inch diameter X 5 inch rusty steel rods and two 42 inch X 6 inch X 0.003 inch gauge rusty steel coupons. About 1.32 ml (0.04 wt. percent) of distilled water was added and the entire contents of the bottle thoroughly agitated at the start of the test period. In Example 13 an additional 0.4 wt. percent of water was added to the bottle after 1 day. The capped bottles were pennitted to stand for 5 days after which visual observations of the steel coupons, the solvent and the surface of the solvent were made and recorded. The bottles were then uncapped and any detectable objectionable odor noted.

The results of the tests are included in Table IV.

TABLE, IV

Color of Solvent Mg. Zinc Loss Soxhlet Condenser The superiority of the composition of this invention in stabilizing methylene chloride on exposure to water and rusty steel storage conditions is evidenced by the results of Example 15 as compared to the results of the tests in Examples 13 and 14 in which two different stabilizing compositions known in the art were used. In Example 15 no uncharacteristic odor was detected but both Examples 13 and 14 had an objectionable putrid odor.

In Examples 16 and 17 respectively, of Table V, 15 ml of substantially water free methylene chloride and methylene chloride stabilized with the specified quantities of diisopropylamine, N-methyl pyrrole, propylene oxide, butylene oxide, methyl acetate, acetone, tertiary amylenes and methyl alcohol were placed in glass vials containing a 1 cm aluminum coupon one sixty-fourth inch thick. The vials were tightly capped and allowed to stand at ambient conditions. After 16 hours no STABILITY STORAGE TESTS OF METHYLENE CHLORIDE Color and Appearance After Test Period Example Stabilized Solvent Days No. System. Wt. Test Solvent and Surface Condition Steel Coupons 13 Methylene Chloride 5 Clear, light yellow; water ring Slightly increased Containing at surface rusting v 0.50 Propylene Oxide 0. l0 Nitromethane 2.30 Dimethoxymethane l4 Methylene Chloride Clear, yellow; yellow band and Increased rust and Containing water ring at surface blisters 1.0 Nitromethane 2.3 l,4-Dioxane l5 Methylene Chloride 5 Clear and Colorless;' water ring Slightly increased rust,

' blackened Containing at surface 0.0025 Diisopropylamine 0.0050 N-Methyl pyrrole 0.25 Propylene Oxide 0.125 Butylene Oxide 0.20 Methyl Acetate 0.05 Acetone 0.25 Tcrt. Amylenes 0.05 Methyl Alcohol changes had taken place in the appearance of the solvent, the pH or the aluminum in each vial. Toluene in an amount of 5 percent by volume and about 0.04 grams of anhydrous aluminum chloride were then added to each vial, the contents stirred, changes in the contents recorded, and the vials loosely capped and allowed to stand. After 4 hours and after 22, changes in the appearance of the aluminum coupons and the solvents, and relative pH values of the solvents, were recorded. The procedure of Examples 16 and 17 was followed in Examples 18 to 22 of Table V. In the latter Examples various compounds reported in the prior literature to be useful in stabilizing chlorinated solvents were evaluated for their ability to stabilize methylene chloride. In Examples 18 to 22 after the tightly capped vials had been standing for 16 hours no changes had occurred in the appearance of the solvent, the pH or the aluminum coupons and the toluene and AlCl were added. The results of the tests of Examples 18 to 22 are set forth in Table I.

TABLE V Table V show that various compounds frequently used as solvent stabilizers are not as effective as the stabilizing composition of this invention in inhibiting degradation of methylene chloride by reaction of aromatic compounds with methylene chloride in the presence of metals, metal salts, and combinations thereof.

Although the present invention has been described with detailed reference to specific embodiments thereof, it is not intended to be so limited since modifications and alterations may be made therein which are within the complete intended scope of this invention as defined by the appended claims.

What is claimed is:

1. A stabilized composition consisting essentially of methylene chloride and from about 0.001 to about 2.0 percent by weight of each of diisopropylamiiie, N- methyl pyrrole, butylene oxide, propylene oxide, methyl acetate, acetone, tertiary amylenes, and methyl alcohol.

2. The composition of claim 1 wherein diisopropyl- INHIBITION OF REACTION OF AROMATIC COMPOUNDS WITH METHYLENE CHLORIDE Upon Addition of 5% Vol.

Example Solvent Toluene and 0.04 grams After After No. System Aluminum Chloride 4 hours 22 hours 16 Methylene Chloride Light Yellow Precipitate Dark Orange No Change Containing Aluminum pH 3 Coupon I-ICI fumes l7 Methylene Chloride Solution Colorless White Precipitate No Change Containing Aluminum Yellow-White Precipitate Colorless pH Coupon, Stabilized about 8.5 With 0.0025 Wt.% Diisopropylamine 0.005 Wt.% N-methyl pyrrole 0.25 Wt.% Propylene Oxide 0.l25 Wt.7z Butylene Oxide 0.20 Wt.% Methyl Acetate 0.05 Wt.7z Acetone 0.25 Wt.% Tert.Amylenes 0.05 Wt.72 Methyl Alcohol l8 Methyl Chloride Solution light brownv Solution light gray- No Change Containing Aluminum Purple Precipitate tan Brown spots Coupon, Stabilized with Turned purple-brown after on aluminum coupon 2.8 Wt.71 Dimethoxya few minutes Grey-white methane precipitate pH 3 l9 Methylene Chloride Solution Dark Solution Purple- Black Precipitate Containing Aluminum Purple Colored Blaclt and Solution Yellow- Coupon, Stabilized Precipitate pH Green pH about With 0.7 Wt.7 about 3.5 4.5 Methyl Butynol 20 Methylene Chloride Light Lavender Precipitate Solution Dark Gray pH about 4.5

Containing Aluminum and Precipitate Coupon, Stabilized Present pH 3 With 2.8 Wt./

l,lDimethoxyethane 21 Methylene Chloride Yellow Green Precipitate Yellow Precipitate White precipitate Containing Aluminum On Aluminum Coupon Solution Yellow Coupon. Stabilized Solution Green-Gray pH about 4.5 with 2.0 Wtf/r pH about 3.5 l ,3-Dioxolane I 22 Methylene Chloride Red Precipitate Orange Precipitate Pink brown Containing Aluminum On Aluminum Coupon Precipitate Coupon, Stabilized Solution Colorless Solution Colorless With 0.8 Wt.7( pH about 4.0 pH about 4.5 1.4-Dioxunc From Table V it will be readily observed that after 4 hours the methylene chloride without the stabilizing amine, N-methyl pyrrole, butylene oxide, propylene oxide, methyl acetate, acetone, tertiary amylenes, and

composition of this invention had undergone a degra- (6 methyl alcohol are each present in the range of 0.002

dation reaction resulting in a dark orange coloration, evolvcmcnt of hydrogen chloride gas and complete loss of utility of thc solvent. Examples 18 to 22 inclusive of to 1.0 percent by weight. 

1. A STABLIZED COMPOSITION CONSISTING ESSENTIALLY OF METHYLENE CHLORIDE AND FROM ABOUT 0.001 TO ABOUT 2.0 PERCENT BY WEIGHT OF EACH OF DIISOPROPYLAMINE, N-METHYL PYRROLE, BUTYLENE OXIDE, POLYLENE OXIDE METHYL, ACETATE ACETONE TERTIERY AMYLENES, AND METHYL ALCOHOL.
 2. The composition of claim 1 wherein diisopropylamine, N-methyl pyrrole, butylene oxide, propylene oxide, methyl acetate, acetone, tertiary amylenes, and methyl alcohol are each present in the range of 0.002 to 1.0 percent by weight. 